FIELD OF THE INVENTION
The present invention pertains to an apparatus and a method of producing a honeycomb body, in particular a catalyst carrier body for catalytic converters, from at least one stack of a plurality of at least partially structured metal sheets.
Catalytic converters are used to reduce the amount of pollutants in exhaust gases, in particular in motor vehicle exhaust gases. The carrier bodies in such catalytic converters may be metallic honeycomb bodies. Such honeycomb bodies are formed of a stack comprising a plurality of at least partially structured metal sheets. U.S. Pat. No. 4,923,109 discloses a honeycomb body with a stack twisted in opposite directions about itself and about a central region.
Furthermore, U.S. Pat. No. 5,135,794 (int'l publication WO 90/03220) discloses a metallic catalytic converter carrier body which is constructed from at least partially structured metal sheets. That catalytic converter carrier body includes at least three stacks of metal sheets, wherein at least three of the stacks are folded about a respective associated bend line in the central region of the honeycomb body and are twisted in the folded condition region with the bend lines.
Apparatuses are known for the production of such honeycomb bodies. Generally, these apparatuses comprise a forked winding device which engages each stack and rotates about an axis, and former segments which close to constitute a former. The internal contour of the closed former corresponds to the external contour of the honeycomb body after winding. In order to ensure winding of the stack or stacks about itself or themselves and about a central region, the former segments are moved towards the stack in such a way that, during the rotary movement of the forked twisting device, the stack or stacks bear against the edge of the former segments and that edge forms a support means. Towards the end of the production procedure the former is completely closed and thus imparts to the honeycomb body its final form.
The prior art apparatuses have two segments which are movable towards and away from each other along a straight line.
During the closing procedure there is the risk that at least one former segment may move in opposite relationship to the direction of movement of the portion of the stack, which is still to be twisted. If the former segment moves against the stack portion, that can result in undesired deformation of the stack or stacks. Such deformation can have the result that individual metal sheets of the stack are partially buckled. The deformation of the metal sheets influences the structure of the honeycomb body. On the one hand the strength of the honeycomb body suffers from such deformation phenomena and on the other hand there is a local variation in the passage cross-sections. Such variations in the passage cross-section give rise to irregular distribution of the exhaust gas profile through the honeycomb body, which may affect the catalytic efficacy of the honeycomb body.
Conventional honeycomb bodies are predominantly circular in cross sectional. The production of other cross-sections requires different production methods. Such a production method is known for example from U.S. Pat. No. 4,519,120. That production method provides that a honeycomb body is first wound and then deformed with certain tools.